People might be better off maximizing memory they have, given the relative instability that can result from the 3 GB switch. You can turn off services that are unneeded while gaming, such as Routing and Remote Access, and processes, such as contact managers and background defraggers. There are several utility packages (System Mechanic comes to mind) that make this easier to do, but Gamebooster 3, which I mentioned above, does it as well, and you can certainly do it on your own. You just have to be careful, and think through in advance what services aren't needed.
Just to verify... I tried doing the suggestion from the original post, and it had VERY undesirable effects on my XP system. To be clear, I am NOT blaming anyone for those problems, just that they occurred. I followed the simple directions, making the adjustments, saving the file as asked... and the system went into a complete fit. Desktop icons disappeared, programs stopped working, it was an absolute nightmare. Simple solution, just undo the entire process. Several re-boots and file checks, everything is back as it should be.
My advice, DO NOT use the original post suggestion.
Game Booster 3 works wonders. Simple install, simple interface, great results. Best of all... any changes that you ask it to do, all get reversed when it is shut off. There is no remembering where the file is that you adjusted, what was the code that you typed, waiting on re-boot after re-boot, missing icons or programs getting monkeyed up... just simply on when you need it, off when you don't.
My criticism isn't meant to come across as harsh towards the original poster... but my experience with the suggestion... was less than pleasant.
Have a blessed day,